Share-Based Payments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2015	Jan. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 657	$ 941	$ 2,284	$ 1,968
General and Administrative Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	474	866	1,530	1,686
Selling and Marketing Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	114	63	447	189
Research and Development Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	65	4	267	19
Translational Oncology Solutions Cost of Sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	2	2	20	12
Personalized Oncology Solutions Cost of Sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2	$ 6	$ 20	$ 62